bash tricks

another useful one is <(cmd here)

It's like $(cmd here) but instead of returning the output of the command as a string passed into the arguments, it makes a new file descriptor for the output of the command and returns the path to it, for use in commands that want a file as an argument.

So for example if you want to use diff to compare your local passwd file to a remote one..

diff -u <(ssh host1 cat /etc/passwd) /etc/passwd

Admittedly I can't think of many things I've used this for outside of diff and alternatives to diff..but I've used it there a lot, like comparing the results of running two slightly different queries.